>>718020004
I wouldn't say it was a miracle. The other homo species were very closely related to us and they exist within our DNA still. Asians and Whites still have Denisovan and Neanderthal DNA. It's more like the less fit versions of modern humans died off as our build edged them out.

And it's not like the older species went extinct either. They just turned into us as they adapted to their new way of life. Every species goes through evolution constantly. There is no species that has been around for more than a couple million years at most. There are genuses that have existed for a long while, like the tuatara, coelacanth, and horseshoe crab, but they undoubtedly are not the same species that existed hundreds of millions of years ago.

>>713944505
I'd reckon that large mammals probably didn't exist at the time because they would've been easy pickings for dinosaurs. Mammals would've had to be arboreal or else they'd need to burrow like moles.

But I could see some getting as big as orangutans or chimpanzees. Maybe 150 - 200 lbs on the heavy side.